Secretion and Endocytosis Flashcards
How do vesicles form and insure they are carrying the correct things?
Coat proteins act to select cargo and to induce the curvature of the cell membrane that leads to the vesicle budding off from the original membrane of the secreting organelle (ex: of coat protein is clathrin)
What is the secretory pathway?
Default pathway for molecules in cell
ER –> Golgi —> lysosomes, secretory vesicles, or the cell membrane
How do vesicles get to the correct target organelles?
Rab-GTP protein on vesicles interacts with specific tether on target organelle which docks the vesicle, then v snares (vesicles snares) and t snares (target snares) form a helix which drives the fusion of the vesicle and the cell membrane
What is glycosylation?
addition of sugars to a molecule that happens in ER and Golgi
What is the difference between N and O linked glycosylation?
N linked: happens in ER, short sugar added to Asparagine, important for protein folding, and targeting, used to fuse sperm and egg
O linked : in Golgi, addition of long disaccharide, attaches to serine, critical for the functioning of connective tissue
What is the function of lysosomes?
to digest molecules in the cell, low pH via proton pump activates enzymes in lysosome to degrade
What targets molecules to lysosome?
manose 6 phosphate, phosphate added in cis Golgi by GlCNac phosphotransferase
What is I cell disease?
Mutation that causes GlcNAC phosphotransferase to be non functional, this means that enzymes cannot get to lysosomes so lysosomes cannot break down part and so get really big; generally get motor function problems, enlarged liver and spleen, hook like hands, and eventual neural degeneration and death by around 6
What are the difference between lysosomes and secretory vesicles?
Secretory vesicles don’t degrade, rather they accumulate materials and wait for a signal from the outside of the cell to release the contents at the cell membrane
How does fusion of secretory vesicles with cell membrane function?
Snares work at cell membrane, but usually mediated by a clamp protein that lets secretory vesicles hang out at cell membrane before being exocytosed. With triggers like high intracellular calcium, the clamp proteins leave and the secretory and cell membrane fuse
What is a hemophagotic syndrome?
Secretory vesicles can’t fuse with the plasma membrane, mutations in Rab and Snare proteins, generally effects NK and CTL cells that want to release materials that can apoptose infected cells, cannot do this because can’t fuse secretory vesicles with cell membrane so have a prolonged immune response which kills people (cytokine storms)
What is phagocytosis?
binding of foreign object on outside of cell, engulfs via actin polymerization, sent to lysosome for degredation (eg macrophages)
What is pintocytosis?
endocytosis of small amt of fluid or plasma membrane, clathrin coat protein picks molecule and allows cell to take up molecule and receptor, pH of vesicles lower, receptor and molecule seperate and can be seperately targeted (degrade molecule and recycle receptor or degrade both)
What causes muscular distrophy?
distruption between cytoskeleton and cell membrane that leads to damage of membrane, influx of Ca and cell death, usually happens first in cells that recieve a lot of mechanical stress like muscle cells
